Alkylphenol disulfonates have been found to be useful as heavy-duty, detergent-active materials. These materials have been prepared in the past by sulfonating alkylphenols in which the alkyl groups have from about 16 to 22 carbon atoms with a sulfonating agent such as oleum, sulfuric acid, chlorosulfonic acid, etc., the sulfonating agent being employed in sufficient quantity to effect substantial ring disulfonation of the substituted phenol. The final material will contain an average of from about 1.5 to 2.0 sulfonic acid groups per molecule. In order to produce an effective heavy-duty detergent from the acidic material, it has been conventional to neutralize the disulfonic acid mixture with a water-soluble, salt-forming cation. It has been common to employ alkali metal and particularly sodium or potassium ions in the form of their oxides or hydroxides to neutralize the acids. In general, relatively weak solutions of the base (i.e., 10 to 25%) have been used, as the excess water was thought to aid in avoiding production of excessive temperatures in the reaction product which might have the effect of producing undesirable color in the product. In detergent production, it is important that color formation be avoided, as materials having low color (i.e., white or near white) are preferred by those using detergent powders, and the presence of excess color may cause coloring of the fabrics to be washed.